DESCRIPTION: Hepatitis C virus (HCV) infection is a major cause of chronic disease leading to cirrhosis, end stage liver disease and hepatocellular carcinoma. Chronic hepatitis C is the leading indication for liver transplantation at the University of Washington Medical Center. Preliminary studies have indicated that infection is typically manifested by persistence of high titered viremia suggesting high levels of ongoing viral replication for prolonged periods of time in these patients. However, despite the increased levels of viral RNA in serum, the outcome of HCV infection in these patients closely resembles the clinical course of HCV infection in the non-transplant setting in several important ways, including the development of chronic active hepatitis in about 50% of cases, development of asymptomatic infection in up to 40% of cases, and manifestations of extra hepatic immune complex disease in up to 10% of cases. These findings support the use of the liver transplant recipient as a model of understanding the relationship between viral replication and clinical disease in humans. This proposal will test the hypothesis at the level of HCV replication in liver, as reflected by quantity of viral RNA and viral antigen, is related to the extent of hepatocellular injury, using 200 sequential liver biopsy specimens obtained prospectively from 20 liver transplant recipients with recurrent HCV and 20 control transplant recipients with asymptomatic HCV infections. Viral genomic and replicative intermediate RNA will be assessed by quantitative competitive PCR and in situ hybridization, and viral NS3 antigen will be assessed by immunohistochemistry. The applicant states the proposal will also test the hypothesis that the tissue distribution and clonal diversity of HCV quasispecies variance is related to the onset and histologic course of post-transplant liver disease in 40 consecutive patients. Distribution of individual HCV quasispecies species traced in serum, liver and peripheral blood mononuclear cells will be evaluated by heteroduplex gel shift analysis of the envelope hypervariable region (HVR1). Quasispecies clonal diversity will be assessed by single strand conformation polymorphism (SSCP). The investigators will test the hypothesis that the patients that develop symptomatic post-transplant liver disease show rapid changes in HCV quasispecies immediately following liver transplantation, with evidence of efficient primary infection of liver allographs prior to the onset of acute hepatitis, while patients who develop asymptomatic post transplant HCV infection show little change in HCV quasispecies diversity.